1. Field of the Invention
The present invention relates generally to the field of electrical control apparatus, and particularly to means for preventing electric hazard.
2. Description of the Prior Art
In order to comply with safety regulations which require that the absence of voltage should be verified before undertaking work on an electrical line or an electrical installation, unipolar alternating voltage detectors are known which essentially comprise a supply source, an assembly of electronic circuits, and an acoustic and/or optical member capable of indicating the presence of a dangerous voltage on a conductor. These component elements are accommodated in an insulating case which normally carries, on its upper portion, a contact member or probe enabling an electrical connection to be established between the apparatus and a conductor the voltage state of which it is desired to verify, and, at its base, a means enabling it to be fixed to an insulating pole.
In their conventional form, these apparatuses have numerous disadvantages of a mechanical and electrical nature. In particular:
ACCESSIBILITY OF THEIR INTERNAL PARTS, INCLUDING THE SUPPLY SOURCE WITH A VIEW TO SIMPLE REPLACEMENT, IS OFTEN POOR AND REQUIRES THE DISMOUNTING AND REMOUNTING OF SEVERAL SCREWS OR MECHANICAL PARTS WHICH INVOLVES RISKS OF LOSS OR ERROR IN RE-ASSEMBLY; AND
THE SEATING OF THE SUPPLY SOURCE IS OFTEN IN THE FORM OF A MORE OR LESS DEEP CAVITY WHICH IS DIFFICULT TO CLEAN IN THE EVENT OF A LEAKAGE OF ELECTROLYTE.
All these disadvantages are considerably increased and their solution is made more difficult when the users require that these apparatuses should be able to be introduced through narrow apertures, which makes it necessary to reduce their width and to increase their length.
Moreover, the known apparatuses are ill-suited for certain particular conditions of use, such as the verification of the absence of voltage at the capacitive terminals which are customarily provided at probe junctions in dry, high-tension cable installations. These terminals are protected by an insulating stopper which has to be removed before the operation and replaced afterwards, and this has customarily necessitated the use of an appropriate instrument.